The invention relates generally to steam turbines, gas compressors, or any device with a rotating shaft that penetrates multiple pressurized casings and has a bearing between those casings. More particularly, the invention relates to increasing the pressure in the vicinity of the bearing between multiple casings to reduce the leakage from the casings around the shaft.
Current turbo-machines such as steam turbines often employ multiple casings with bearings residing in stationary standards between the casings. In current practice, the bearings operate in an environment of atmospheric air. Operating the bearing at atmospheric pressure requires the higher pressure gas or steam within the casing to be sealed against a pressure difference equal to the gauge pressure present at the end of the casing. To contain the gas or steam within the casing, each casing includes a series of non-contacting gland seals, referred to as an end packing. Each end packing includes a number of non-contacting seals such as leaf seals, brush seals, labyrinth seals, etc., that partially seal against the rotating shaft of the steam turbine. Due to the finite clearance in these seals there is an inevitable leakage of gas or steam that results in lost potential to produce rotating shaft work in a turbine or increased shaft work required in a compressor. The rate of leakage is dependent upon the seal geometry, clearance, and pressure difference between the gas or steam inside the casing and the air outside the casing.